The accumulation of residues on dental appliances (e.g., removable braces, retainers, night guards, removable braces, dentures, etc.) is a familiar and persistent problem for wearers of such appliances. These residues often consist of some combination of food particles and biofilm (i.e., plaque), the latter of which is a slime layer that naturally develops when bacteria attach to an inert support. Many of these bacteria produce volatile sulfur compounds as waste products. If the dental appliance is not rid of food particles and biofilm on a regular basis, the malodourous waste products will accumulate, causing the wearer to exhibit bad breath. Even more serious is the potential for pathogenic bacteria to inhabit the biofilm, increasing the likelihood of infection for the wearer.
The majority of commercially available effervescent dental appliance cleansing tablets are based on alkaline peroxysalts (e.g., those sold under the tradename EFFERDENT), which provide excellent bleaching action but poor plaque removal, as described in U.S. Pat. No. 4,552,679. An additional shortcoming of alkaline peroxysalts is their documented health risk. After seventy-three severe reactions and at least one death, the U.S. Food and Drug Administration issued a statement on Feb. 14, 2008 asking the manufacturers of denture cleansers to revise labeling and to consider appropriate alternatives to persulfate, a common alkaline peroxysalt found in many brands, including EFFERDENT. All peroxysalts share a common mode of operation (i.e., liberation of hydrogen peroxide upon contact with water) and a similar structural feature (i.e., an associated molecule of hydrogen peroxide). Therefore, it is an object of the present invention to provide a dental appliance cleansing composition that does not include peroxysalts. Examples of powders and tablets incorporating alkaline peroxysalts can be found in U.S. Pat. Nos. 4,362,639, 4,552,679, and 5,486,304, and U.S. Patent Application 20070054830.
U.S. Pat. No. 8,044,008 to Muzik et al (“the Muzik composition”) represents the most efficacious prior art composition. A shortcoming of the Muzik composition, however, is a high concentration of a chloramine bleaching agent, namely from 1 percent to 20 percent by weight of the composition. Upon dissolution of the composition in water, a pH-dependent equilibrium is established between the chloramine bleaching agent, hypochlorous acid, and hypochlorite ion. However, upon dissolution of the composition in water, hypochlorous acid also imparts a chlorine-like odor that is reminiscent of swimming pools. Muzik et al. teach the use of a fragrance at up to about 3 percent by weight of the composition “to mask any chlorine odor originating from the dental appliance cleansing formula.” Unfortunately, high liquid fragrance loadings (greater than about 1.5 percent) can introduce aggregation of solids in the formula (“caking”) and slow dissolution. In addition, fragrance represents one of the most expensive raw materials costs in the manufacture of the composition. Therefore, a need persists for a composition that is effective at disinfecting and removing biofilm from dental appliances without suffering from the shortcomings of chlorine-like odor and/or the requirement for high fragrance loadings.